In general, bolometers implemented using MEMS technology are typically provided with a very thin layer or film which serves as an absorber for the bolometer. The absorber is formed of a material which is capable of absorbing energy from incident infrared radiation and is provided in a substrate in a manner that maximizes exposure to infrared radiation while minimizing thermal loss to the substrate.
A transducer having an electrical resistance that varies with temperature is provided in thermal contact with absorber. Infrared radiation incident upon the bolometer will be absorbed by the absorber element of the bolometer and the heat generated by the absorbed radiation will be transferred to the transducer element. As the transducer element heats in response to the absorbed radiation, the electrical resistance of the transducer element will change in a predetermined manner. By detecting changes in the electrical resistance, a measure of the incident infrared radiation can be obtained.
A current must flow through the transducer element of the bolometer in order for the transducer element to function as a resistor and exhibit temperature dependent resistance changes. The requirements imposed by MEMS technology on the fabrication process have limited the ability to incorporate switching mechanisms into bolometer devices for controlling the flow of current to the bolometer. As a result, current may flow through the transducer element continuously when the device is powered so that power is consumed at all times, even in a standby mode when the device is powered on but not being used to detect temperature.
Furthermore, not being able to effectively switch individual MEMS bolometers ON/OFF can limit the functionality of certain devices, such as infrared cameras and thermal imaging sensors, where multiple bolometers are provided in arrays to serve as pixels of an image sensor. The selective reading out of the temperature values indicated by the bolometer pixels is performed by evaluation circuitry which is typically implemented separately using CMOS technology on a semiconductor chip.